1. Field of the Invention
In one aspect, this invention relates to an anionic waterflood additive.
In another aspect, this invention relates to a process for the recovery of hydrocarbons from a petroliferous formation involving injecting into a petroliferous formation an improved anionic waterflood additive plus water.
2. Brief Description of the Prior Art
A large percentage of the oil in petroliferous formations is held within the rock of the formation by the surface forces between the formation rock, the oil therein, and the aqueous liquid in the formation. As a result, a substantial portion of such oil usually remains in the formation even when the wells traversing the formation are no longer productive. Various secondary recovery techniques, such as thermal recovery, gas injection, and waterflooding have been suggested for the recovery of this fixed oil which remains in the formation after primary recovery methods are no longer feasible to produce additional oil. As a secondary recovery technique, waterflooding is quite commonly employed, and a multiplicity of methods have been suggested for improving efficiency and economy of oil recovery by the practice of waterflooding. Such methods frequently include incorporation of a water-soluble surfactant in the waterflood liquid which is injected into the petroliferous formation. A number of typical surfactants have been proposed for this purpose, including alkyl pyridinium salts, sodium lauryl sulfate, certain sulfonates, glycosides, sodium oleate, quaternary ammonium salts, and the like. The use of such surfactants has arisen because it is widely recognized that a low interfacial tension between the surfactant flood water and the reservoir crude oil is beneficial to the improvement of recovery efficiencies and feasibilities.
Recently, it has been proposed that nonionic surfactant solutions, such as a polyoxyethylene-polyoxypropylene copolymer containing solution be injected into the formation through a first of a series of two well bores to thereby displace the hydrocarbons in the formation toward a second well bore. The nonionic surfactant flood is then followed by an injection of a slug of aqueous caustic mixture into the formation through the first well bore to displace the hydrocarbon of the formation and the injected surfactant toward the second well bore. The caustic slug has a basicity of at least 1.5 pH levels greater than that of the native formation waters. However, use of a nonionic surfactant has not fully met the needs of the industry as a desirable waterflood surfactant composition, and new compositions are constantly being sought which will allow recovery of the residual oil remaining in the formation following primary oil recovery operations. Also, the surfactant materials of the prior art have on occasion suffered from lack of availability or from nonfeasibility due to excessive costs, and thus have not entirely satisfied the long-felt need of the industry for a feasible method to recover oil remaining in subterranean petroliferous formations.